The invention relates to a picture display device having a flat vacuum envelope which is provided with a transparent face plate with a luminescent screen and with a rear wall, said display device comprising an electron supply section for emitting electron currents, and an active selection electrode section having first, preselection, electrodes and second, fine-selection, electrodes, located closer to the screen, for directing a plurality of electron currents towards desired positions on the luminescent screen.
The display device described above may be of the flat-panel type, as disclosed in EP-A-464 937, or of another flat-panel type in which electron currents parallel to a display screen are emitted and deflected towards predetermined positions on the display screen. Display devices of the flat-panel type are devices having a transparent face plate and, arranged at a small distance therefrom, a rear plate, in which the inner surface of the face plate is provided with a (for example, hexagonal) pattern of phosphor dots. If (video information-controlled) electrons impinge upon the luminescent screen, a visual image is formed which is visible via the front side of the face plate. The face plate may be flat or, if desired, curved (for example, spherical or cylindrical).
The display device disclosed in EP-A-464 937 comprises a plurality of juxtaposed sources for emitting electrons, local electron propagation means cooperating with the sources and each having walls of a high-ohmic, electrically substantially insulating material having a secondary emission coefficient suitable for propagating emitted electrons along the wall, and an addressing means comprising an active selection electrode section having (first) electrodes (preselection electrodes) which can be driven row by row so as to extract electrons from the propagation means at predetermined extraction locations facing the luminescent screen, further means being provided for directing extracted electrons towards pixels of the luminescent screen for producing a picture composed of pixels.
It is known from EP-A-464 937 to arrange an apertured fine-selection plate, whose apertures are addressable by means of second, or fine-selection electrodes between the first electrodes and the screen. The arrangement is such that each extraction location of the addressing means is associated with at least two apertures in the fine-selection plate. The selection electrode section is thus of the multi-stage (in this case two-stage) type. This means that the fine-selection electrodes can be divided into groups and that the corresponding fine-selection electrodes of two or more groups can be coupled to each other. In fact, a preselection has already taken place and electrons can no longer land on a wrong phosphor element arrangement (phosphor triplet). This means that the drive can be simplified because the number of drives can be reduced.